1. Field of the Invention
The present invention relates to the transmission of power from a drive motor, the motor having a rotatable output shaft, to a tool or other load and, particularly, to the mechanical imparting of rotary power to a tool while simultaneously supplying electrical power and/or hydraulic or pneumatic fluid to the tool. More specifically, this invention is directed to a mechanical drive characterized by volumetric efficiency and especially to a drive system comprising a planetary gear unit which is arranged concentrically with respect to a hollow shaft. Accordingly, the general objects of the present invention are to provide novel and improved methods and apparatus of such character.
2. Description of the Prior Art
The present invention relates to a class of power generation and transmission devices known in the art as "geared motors". While not limited thereto in their utility, such devices are particularly well suited for use in robotic applications where they are often referred to as "hand gears" and are employed to move tools such as, for example, for the purpose of gripping, welding, deburring, applying adhesive, painting, etc. In such applications the geared motor, i.e., the torque generator and associated drive train, causes the tool to rotate about an axis of rotation, which typically will be angularly related with respect to the axis of rotation of the output shaft of the motor which generates the torque, and to also to function as a "wrist joint" to pivot the tool about a swivel axis. The swivel axis will customarily be oriented transversely with respect to the axis about which the tool is rotated. In other words, an objective in the design of many geared motors is to simulate the movements an operator would, if present, impart to the tool thus permitting the tool to function where a human operator can not be present because of space or environmental restrictions.
It is common practice to include, in a geared motor, an overload clutch between the rotatable load, i.e., the driven tool, and the output of the drive train. The provision of such an overload clutch normally ensures a rigid connection between the tool and geared motor unit while defining a flexible connection which prevents damage due, for example, to the tool colliding with a workpiece. In order to deliver electrical power to the clutch and/or pressurized hydraulic or pneumatic fluid to the tool being manipulated, means must be provided for routing electrical conductors and/or conduits through the geared motor unit. By way of example, if the geared motor unit is employed to manipulate a spray paint nozzle, the conduit for delivering the paint to the nozzle should desirably be routed through the geared motor unit. There are also instances where it would be desirable to provide an auxiliary tool drive at the end of a robotic arm without physically loading the hand gear with the additional weight of the motor of the auxiliary drive. This, however, would require the provision of some means for delivering longitudinal or rotary motion through the geared motor unit to the tool. The prior art has not offered a satisfactory solution, and particularly a volumetrically efficient solution, for establishing a path for the delivery of power and/or operating fluid through a geared motor or hand gear.